Reaction product of cellulosic material



Patented Nov. 2, 1937 UNITED STATES PATENT o F cs 2,098,082 REACTION PRODUCT F CELLULOSIC MATERIAL Albert Henry Bowen and Theodore Williams Dike, Seattle, Wash., assignors to I. F. Laucks, Inc., Seattle, Wash., a corporation of Washington No Drawing. Application November 19, 1934, Serial No. 753,648

6 Slaims.

action between zinc chloride, urea, and formal- 10 dehyde, said compound being the subject of our co-pending United States application Serial No. 666,930, filed April 19, 1933, now Patent No. 1,992,180, of which this application is a continuation in part. We have found that new and useful properties result whenever cellulosic Inaterial is contacted with the foregoing resinous material, and that these properties may be enhanced and modified with great advantage if the treated materials are heated so as to convert the so economically. Examples of our new products, comprise new forms of coated paper, beater sized paper, tub sized paper, dense impregnated paper or cloth articles similar to Micarta, window shade cloth, bookbinders cloth or buckram, vat sized textiles, plywood, edge glued veneerfand similar products.

. In all these products we have discovered the common characteristic that intimate association of cellulosic material with a urea formaldehyde condensation product containing zinc chloride results in remarkably useful properties.

It is of course well known that zinc chlorideis one of the few chemicals that exerts a marked effect on cellulose. We have also found, as shown in co-pending application before mentioned, that it has a profound effect on urea formaldehyde compounds. We believe that the zinc chloride forms a connecting link as it werebetween the urea resin and the cellulose.

To the accomplishment of the foregoing and related ends, the invention, then comprises the features hereinafter fully described, and partic-, ularly pointed out in the claims, the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative however, of but few of the various ways, 5 in which the principle of the invention may be employed.

Example 1.For example, coated or sized paper may be produced as follows: A liquid condensation product is made by reacting together 10 The zinc chloride is dissolved in the formalin, the urea added and the mixture heated to 175 F. for thirty minutes and then cooled to room temperature. A moderately viscous, water soluble, clear, stable liquor is the result. 100 lbs. of china clay are then mixed with 70 lbs. of water and 45.6 lbs. of the liquor stirred in. Preferably 0.5 lb. of papermakers alum is stirred in. The resulting size or coating mixture is coated on the paper by means of the customary coating apparatus and the paper dried.

The product has remarkable printing properties, taking clear impressions from much finer photo-engravers screens than can be used with casein coated paper. There is complete-freedom from foam and resulting blemishes. Curling of thepaper is decidedly reduced. The paper is whiter than that which can be made using casein and feels smoother. 'Ui'ilike casein coatings this coating does not deteriorate or decompose with "age. The paper shows high adhesion of the coating and takes printing ink without picking, besides showing about treble the resistance of casein bound coated paper to the wet rub test. Furthermore, if the coated paper of our inven- 40 tion is calendered with hot rolls, the resin coated cellulose fibers become converted to a still more insoluble condition, with marked improvement in surface gloss, printing properties and durability. The properties of the coated paper may also be modified by a variety of additions and substitutions, including the use of plasticizers, substitution of other fillers, coloring agents, etc. Notwithstanding the presence of zinc chloride in large amount in the foregoing coating mixture the resulting paper is not at all hygroscopic. The cellulose of the paper and the zinc chloride containing resin appear to have combined to form a product possessing new properties not present in the components.

Exam le 2. -15 lbs. of fused zinc chloride are dissolved in 900 lbs. of commercial 37% formalin, and 375 lbs. of urea are then dissolved in the mixture. As soon as solution is complete the mixture is filtered. It is then placed in a conainer provided with stirring mechanism and provision for cooling. Stirring is continued for six hours with sufficient cooling to prevent the temperature of the reacting mixture from rising above F. After about four hours an abundant white precipitate appears and the mixture changes to a mush which is very soluble in cold water. A desirable addition to the reaction mixture is about 195 lbs. of glucose as a plasticizer. This addition may be made without materially aifecting the progress of the reaction.

112.5 lbs. of thin boiling starch are then dissolved in 525 lbs. of hot water, cooled and added to the foregoing mush.

Then to each lbs. of the foregoing solution 900 lbs. of water are added and the resulting solution treated with 0.2 lb. oxalic acid. This solution, containing approximately 5% of solids, is used as a tub size in the usual manner.

The resulting paper, if made from free or fast short beaten stock acquires an exceptional finish upon calendering and has a resistance to the penetration of varnish only obtainable hitherto by means of long expensive beating. This desirable character is also combined with high wet strength. This particular size effects an important economy in the manufacture of varnished billboard paper. In place of the oxalic acid equivalent amounts of other acid providing materials may be used. The effect of the acid is to insolubillze the zinc chloride urea resin as the paper is dried on the machine. The association of the cellulose of the paper and the zinc chloride containing resin results in desirable new properties in the paper not hitherto available, and the result is obtained at a reduced cost with substantial saving in beating time.

Example 3.--Absorbent alpha cellulose paper is soaked in the unprecipitated reaction mixture described in Example 2 with the substitution of about 10% of the urea by thiourea and an addition of diethylene glycol equal to 10% of the weight of the liquor. The glucose mentioned in Example 2 is not included in this reaction mixture. The sheets are then thoroughly dried, superimposed to the desired thickness, and hot pressed at 275 F. and 1000 lbs. per square inch pressure for five minutes for a finished thickness of inch. The resulting product resembles Micarta, is very dense, equals Micarta in strength and resistance to water absorption, with good dielectric puncture resistance and low tendency to surface tracking of the electric current.

Example 4.Window shade cloth may be made as follows: To 200 parts of the liquor described in Example 1 are added 30 parts of finely ground asbestos known as super-floss, and 30 parts of diethylene glycol. The mixture is ground together in a ball mill or by other suitable means. Water may be added to thin the mixture if necessary. This coating when applied to the untreated cotton or linen cloth on one side only, gives perfect one-sidedness. The cloth after drying is made water resistant by heating, preferably by passing through hot calender rolls. The insolubilizing effect may also be obtained by the use of acid as in Example 2.

Example 5.-The coated cloth known as library buckram, which is used for binding books, may be made in the following manner: 5 parts of an inert filler such asfinely ground clay or silica is added to 100 parts of the liquor described in Example 1. Dlethylene glycol 15 parts is then added and any pigment, suchas ultramarine blue 3 parts. The mixture is ground together and applied to the cloth by rolls or brush. After the coated cloth is well dried it is passed through hot calender rolls to convert the resin and resinimpregnated cellulosic fibers to an insoluble state. Acid insolubilizing may also be used.

Example 6.Plywood may be glued as follows; The liquor described in Example 1 is cooked for double the period and then cooled. This increases its viscosity until it can be readily spread on wood veneers by brush or rubber roller mechanical glue spreader. Both sides of birch core plies are then spread with the liquor at the rate of approximately 50 lbs. per 1000 square feet of double glue line. The coated cores are then dried with warm air at not to exceed F. The dried cores may be used at once or within about one weeks time as convenient. The cores are assembled with birch or other face stock and hot pressed using about 200 lbs. hydraulic pressure,

about 320 F. heat and a pressing time of thirty seconds if the face stock is ,5 inch thick. The plywood when tested by standard shear test will give dry shears of around 450 lbs. per square inch, with wood failure of 80% and similar samples soaked in cold water for 48 hours will give practically the same shear test and wood failure, demonstrating the remarkable strength and insolubility of the bond.

Example 7.Edge glued veneer sheets may be produced as follows: A book of thin, costly face veneer is clamped together and the combined edges are jointed to a true, square, straight edge on a veneer jointer. One of the jointed edges is then thinly coated with the mush described in Example 2. The coating is then dried and the veneer separated. Two edges to be Joined, at least one of them glued as above, are brought in contact on the bed of an edge gluing machine provided with means for applying both sideways and downward pressure along the joint together with heat at about 320 F. The pressure and heat is then applied for about one second. The resulting joint will be found as strong as the veneer itself, either in the dry state or when wet, and is colorless and 'invisible ;with a perfect union throughout the entire length. This method completely eliminates the customary veneer tape with its cost and attendant dimculties, permits the use of extremely thin face veneer and has numerous advantages. It is the only method of edge gluing permitting the work to be done with all the parts in a dry condition and no moisture or liquid applied at the time of forming the joint.

Other modes of applying the principle of our invention may be employed, changebeing made as regards the details described, provided the fibrous product coated with a composition embodying urea-zinc chloride-formaldehyde resin.

5. As a new article of manufacture, coated paper embodying an adhesive comprising an urea.- zinc chloride-formaldehyde resin in which resin the amount of zinc chloride is not less than 4% of the amount of the urea.

' 6. As a new article of manufacture. a cellulosic fibrous product embodying an adhesive comprising an urea-zinc chloride-formaldehyde resin in which resin the amount of zinc chloride is not less than 4% of the amount of the urea. ALBERT HENRY BOWEN.

THEODORE WILLIAMS DIKE. 

